CVE-2026-23401: Linux kernel · Use After Free
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 8.1 High · fixed in fd28c5618699180cd69619801e9ae6a5266c0a22 : patch Linux kernel soon.
Data as of 5 Nov 2026, 21:49 UTC
Thin evidence
One scorer or none| ADP (redhat-SADP) | CVSS 3.1 | 8.1 |
|---|
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-05.
- Patch
- Available – fixed in fd28c5618699180cd69619801e9ae6a5266c0a22, ed5909992f344a7d3f4024261e9f751d9618a27d, bce7fe59d43531623f3e43779127bfb33804925d +4
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 1 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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Description
In the Linux kernel, the following vulnerability has been resolved: KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE When installing an emulated MMIO SPTE, do so *after* dropping/zapping the existing SPTE (if it's shadow-present). While commit a54aa15c6bda3 was right about it being impossible to convert a shadow-present SPTE to an MMIO SPTE due to a _guest_ write, it failed to account for writes to guest memory that are outside the scope of KVM. E.g. if host userspace modifies a shadowed gPTE to switch from a memslot to emulted MMIO and then the guest hits a relevant page fault, KVM will install the MMIO SPTE without first zapping the shadow-present SPTE. ------------[ cut here ]------------ is_shadow_present_pte(*sptep) WARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CPU#0: vmx_ept_stale_r/4292 Modules linked in: kvm_intel kvm irqbypass CPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-eafebd2d2ab0-sink-vm #319 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm] Call Trace: <TASK> mmu_set_spte+0x237/0x440 [kvm] ept_page_fault+0x535/0x7f0 [kvm] kvm_mmu_do_page_fault+0xee/0x1f0 [kvm] kvm_mmu_page_fault+0x8d/0x620 [kvm] vmx_handle_exit+0x18c/0x5a0 [kvm_intel] kvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm] kvm_vcpu_ioctl+0x2d5/0x980 [kvm] __x64_sys_ioctl+0x8a/0xd0 do_syscall_64+0xb5/0x730 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x47fa3f </TASK> ---[ end trace 0000000000000000 ]---
References
- git.kernel.org/stable/c/20656cd1f243d3a154aac5dd1b823110b6906fe1 (opens in a new tab)
- git.kernel.org/stable/c/ed5909992f344a7d3f4024261e9f751d9618a27d (opens in a new tab)
- git.kernel.org/stable/c/fd28c5618699180cd69619801e9ae6a5266c0a22 (opens in a new tab)
- git.kernel.org/stable/c/459158151a158a6703b49f3c9de0e536d8bd553f (opens in a new tab)
- git.kernel.org/stable/c/695320de6eadb75aaed8be1787c4ce4c189e4c7b (opens in a new tab)
- git.kernel.org/stable/c/bce7fe59d43531623f3e43779127bfb33804925d (opens in a new tab)
- git.kernel.org/stable/c/aad885e774966e97b675dfe928da164214a71605 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-23401 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2453803 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23401.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:15883 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:19569 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:13936 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:20593 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:13932 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:14339 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:19568 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:13577 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36530 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:14230 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:19521 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36531 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36532 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36533 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:36534 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:13578 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:14137 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:19875 (opens in a new tab)